[rsync]

"So anybody who happens to have a compromised immune system gets to fight your personalised microbes, perhaps fatally?"

Yes, and that is true ipso facto whether they are using soap or not. You will also be fighting the microbes of school aged children (a preschool is one hell of a petri dish), animals (domestic and wild), as well as the entire biosphere you inhabit in general.

If you have a compromised immune system, your neighbors decision to follow a soap-free cleansing regime (which is NOT appealing to me, btw) is the very least of your worries.

[jrabone]

Soap and water is very good at removing faecal contamination. In the absence of small children and pets, and the taking of a prophylactic dose of antibiotics daily, my main concern is whether the people I share work and living space with are spreading their own faeces over surfaces I interact with. If their cleansing regime is as effective as soap and hot water, all is well.

[DanBC]

CDC say soap and not hot water is fine too. They prefer running water.